Handing off a terminal among wireless access points

ABSTRACT

A method and system for handing off a terminal among a plurality of wireless access points (APs) connected to a central management AP. The method comprising: receiving network condition information of a terminal communicatively connected to a first wireless AP among the plurality of wireless APs. Determining a second wireless AP the plurality of wireless APs to which the terminal is to be handed off based on the network condition information of the terminal. The second wireless AP is virtually connected to the terminal. Submitting a handoff request to the second wireless AP. Notifying the terminal to hand off to the second wireless AP in response to receiving a handoff response from the second wireless AP.

CROSS REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. §119, the present application claims priority toChinese Application No. 2013-10524940.6, filed Oct. 30, 2013, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The invention relates to wireless communication, more particularly, to aterminal changing a connection between wireless access points.

BACKGROUND OF THE INVENTION

Currently, wireless communication has become more and more popular.Generally, a configuration for installing a wireless network includeswireless network cards and a wireless Access Point (AP). A wireless APmainly functions as a bridge between wireless work stations and wiredlocal area network (LAN) in a Media Access Control layer (MAC). Withwireless AP, a wireless work station may connect to network quickly andeasily.

With an increase in the use and complexity of wireless networks, thereis often more than one available wireless AP in office area or otherpublic location. Under current technology, generally, a wireless networkcard on a user device will access to a wireless AP based on preferenceorder based on local settings of the work station, e.g., settingregarding whether the wireless AP can be authenticated and currentchannel quality etc. However, when a user is moving in the area, theirchanging location can lead to changes is channel quality and strength ofa wireless AP that their workstation is connected to. At this time, thewireless network card will generally maintain connection with a currentwireless AP to which it is connected, and will access another wirelessAP only after communication is unavailable. In addition, quality of theconnection is usually very poor before handoff (the process of changingfrom one wireless AP to another). During handoff, the connection betweenthe work station and available wireless APs is severed for a shortperiod of time. Thus, the device of the user, e.g., the work station,uses a large amount of power before the handoff due to increased energyrequirements to transmit data. In addition, the speed of communication,before the handoff, is relatively low due to poor channel quality,thereby affecting performance of the whole network.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is provided amethod for handing off a terminal among a plurality of wireless accesspoints (APs), wherein the plurality of wireless APs is connected to acentral management AP. The method comprising: receiving networkcondition information of a terminal communicatively connected to a firstwireless AP in the plurality of wireless APs; determining a secondwireless AP in the plurality of wireless APs to which the terminal is tobe handed off based on the network condition information of theterminal, wherein the second wireless AP is virtually connected to theterminal; submitting a handoff request to the second wireless AP; andnotifying the terminal to hand off from the first wireless AP to thesecond wireless AP in response to receiving a handoff response from thesecond wireless AP.

According to another embodiment of the invention, there is provided asystem for handing off a terminal among a plurality of wireless accesspoints (APs), wherein the plurality of wireless APs is connected to acentral management AP. The system comprising: a receiving moduleconfigured to receive network condition information of a terminalcommunicatively connected to a first wireless AP in the plurality ofwireless APs; a handoff determining module configured to determine asecond wireless AP in the plurality of wireless APs to which theterminal is to be handed off based on the network condition informationof the terminal, wherein the second wireless AP is virtually connectedto the terminal; a handoff requesting module configured to submit ahandoff request to the second wireless AP; and a handoff notifyingmodule configured to notify the terminal to hand off from the firstwireless AP to the second wireless AP in response to receiving a handoffresponse from the second wireless AP.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some embodiments of the presentdisclosure in the accompanying drawings, the above and other objects,features and advantages of the present disclosure will become moreapparent, wherein the same reference generally refers to the samecomponents in the embodiments of the present disclosure.

FIG. 1 illustrates a functional block diagram of an exemplary computersystem/server, which is capable of implementing an embodiment of thepresent invention.

FIG. 2 depicts a diagram of a system for handing off connection betweena terminal and access points (APs), according to an embodiment of thepresent invention.

FIG. 3 depicts a flowchart of a method for handing off a terminal amonga plurality of wireless APs, according to an embodiment of the presentinvention.

FIG. 4 depicts a diagram of an example of a flow of handing off aterminal among a plurality of wireless APs, according to an embodimentof the present invention.

FIG. 5 depicts a block diagram of a system for handing off a terminalamong a plurality of wireless APs, according to an embodiment of thepresent invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide a solution capable ofexecuting automatic handoff among wireless APs. One embodiment of thepresent invention provides a reduced usage of power before the handoff.One embodiment of the present invention provides increased speeds ofcommunication before the handoff. One embodiment of the presentinvention provides increased performance of a communication throughimproved handoff among wireless APs. Embodiments of the presentinvention provide a mobile terminal that is connected to a wireless APsuch that one or more of: i) channel quality is maximized; ii) networkperformance is improved; iii) throughput is increased; iv) powerconsumption is reduced; and v) disconnection during handoff is reduced.Note that as used channel quality refers to the quality of thecommunicative connection between a given AP and a terminal. In someembodiments, such a channel quality includes one or more of signalstrength, rate of data transfer, and other parameters as are known andunderstood by those skilled in the art.

Certain embodiments are herein described in more detail with referenceto the accompanying drawings, in which some embodiments of the presentdisclosure have been illustrated. However, the present disclosure can beimplemented in various manners, and thus should not be construed to belimited to the embodiments disclosed herein. On the contrary, thoseembodiments are provided for the thorough and complete understanding ofthe present disclosure, and completely conveying the scope of thepresent disclosure to those skilled in the art.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readablestorage medium. A computer readable storage medium may be, for example,but not limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium would include thefollowing: a portable computer diskette, a hard disk, a random accessmemory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), an optical storage device, a magnetic storagedevice, or any suitable combination of the foregoing. In the context ofthis document, a computer readable storage medium may be any tangiblemedium that can contain, or store a program for use by or in connectionwith an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java®, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means or modules for implementing the functions/actsspecified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

Referring now to FIG. 1, FIG. 1 illustrates a functional block diagram,10, of an exemplary computer system/server 12, which is capable ofimplementing an embodiment of the present invention is shown. Computersystem/server 12 is only illustrative and is not intended to suggest anylimitation as to the scope of use or functionality of embodiments of theinvention described herein.

As shown in FIG. 1, computer system/server 12 is shown in the form of ageneral-purpose computing device. The components of computersystem/server 12 may include, but are not limited to, one or moreprocessors or processing units 16, a system memory 28, and a bus 18 thatcouples various system components including system memory 28 toprocessor 16.

Bus 18 represents one or more of any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, anaccelerated graphics port, and a processor or local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus.

Computer system/server 12 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 12, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 28 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 30 and/or cachememory 32. Computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 34 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 18 by one or more datamedia interfaces. As will be further depicted and described below,memory 28 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 42 generally carry out the functions and/ormethodologies of embodiments of the invention as described herein.

Computer system/server 12 may also communicate with one or more externaldevices 14 such as a keyboard, a pointing device, a display 24, etc.;one or more devices that enable a user to interact with computersystem/server 12; and/or any devices (e.g., network card, modem, etc.)that enable computer system/server 12 to communicate with one or moreother computing devices. Such communication can occur via Input/Output(I/O) interfaces 22. Still yet, computer system/server 12 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 20. As depicted, network adapter 20communicates with the other components of computer system/server 12 viabus 18. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 12. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

In order to better solve the problem existed during access point (AP)handoff of a terminal, according to embodiments of the invention, thereis proposed to use a centrally managed AP (parent AP) to centrallymanage all other APs (child AP) within a same public area. The parent APcan be connected to child APs through wired or wireless links.

In one embodiment, the parent AP acquires channel quality informationbetween a terminal and different child APs via manner of active scanningor terminal report, and by storing this information in a connectionpool, the parent AP utilizes this information and in conjunction withother information (such as network congest degree etc.) to manage thehanding off of terminals. A method and system according to variousembodiments of the invention will be described below with reference toaccompany drawings.

FIG. 2 depicts a diagram of a system for handing off connection betweena terminal and APs according to an embodiment of the invention.

As shown in FIG. 2, the system comprises a central management AP, i.e.parent AP (AP-A), and a plurality of child APs connected to the parentAP, such as AP-a, AP-b, AP-c, wherein, the parent AP can be connected tochild APs by wired link such as existing wired network, or by wirelesslink such as wireless communication technology like a wireless meshnetwork (WMN).

The terminal is connected to and in communication with one of theplurality of child APs through a wireless network card wc-1, that is,they maintain a communicatively connected relationship. The terminalmaintains a virtually connected relationship with other child APs. Asused herein, a “virtual connection” refers to a physical network card ofthe terminal that virtualizes several virtual network cards. Inaddition, in one embodiment, virtual network cards probe other wirelessAPs to, for example, measure signal quality etc., but do not transferdata. In contrast, one virtual network card is actually connected to andin communication with the wireless AP, such a connection is hereindenoted as a “real connection”. Virtualization of a plurality of virtualnetwork cards on a physical network card and keeping connected withdifferent APs is a technique known in the art (the description of whichis omitted herein for brevity). In this embodiment, through virtualconnections with other child APs, the terminal probes channel quality ofother child APs while maintaining communication with a current child AP.

In this embodiment, there is stored within the parent AP a connectionpool holding connection information of each child AP, as shown intable 1. Table 1 shows an example of a connection pool stored in theparent AP for holding connection information between terminals and childAPs. It should be noted that, channel quality in table 1 is representedby signal to interference plus noise ratio (SINR) and received signalstrength indicator (RSSI). However, the representation may be made byany other manners for representing channel quality as are known to thoseskilled in the art.

TABLE 1 Connection pool of the parent AP (AP-A) Signal to Receivedinterference signal Terminal plus noise strength Connection Terminal MACChild AP AP MAC ratio indicator ID name address name address (SINR, dB)(RSSI, dBm) Xxxx test-23xx 44-45-53- AP-a 34-35-50- 20 −60 54-00-0014-10-21 Xxxx test-23xx 44-45-53- AP-b 12-05-12- 3 −77 54-00-00 34-20-01

In each child AP, there is also stored information of each terminalconnected thereto, and channel quality of each connection, as shown intable 2.

TABLE 2 Information of terminals stored in a child AP (AP-a) Signal toReceived signal Terminal interference strength Terminal Terminal MACplus noise ratio indicator No. name address (SINR, dB) (RSSI, dBm) MS-1test-23xx 44-45-53- 20 −60 54-00-00

In this embodiment, each terminal also stores the information of eachchild AP to which it may be connected and the associated channelquality, as shown in table 3.

TABLE 3 Information of child APs stored in a terminal Signal to Receivedsignal interference strength Real AP AP AP MAC plus noise ratioindicator connection No. name address (SINR, dB) (RSSI, dBm) or not 1AP-a 34-35-50- 20 −60 Yes 14-10-21 2 AP-b 12-05-12- 3 −77 No 34-20-01

Note that in one embodiment, the above information is acquired duringactual operation of the system.

The procedure of establishing communication connection and virtualconnection between a terminal and each AP is further described below. Inthis embodiment, after the terminal is powered on, the terminal searchesfor nearby AP (within communication range), identifies a nearby AP, andis connected to that AP (AP-a) after authentication. Accordingly,connection information is stored in the terminal, as shown in first rowof the above Table 3. In this embodiment, in AP-a, there is also storedconnection information between it and the terminal, as shown in theabove Table 2. At the same time, AP-A acquires and stores connectioninformation regarding the connection between AP-a and the terminal. Thisconnection information is stored in the connection pool throughconnections between the central management AP (e.g., AP-A), and eachchild AP (as shown in first row of the above Table 1). In variousembodiments, the virtual connection between the terminal and other childAPs is created using various processes. For example, the terminalcontinues to search other nearby APs and finds AP-b, and establish avirtual connection therewith. Alternatively, the central management APacquires data identifying the connection between the terminal and AP-avia AP-a. For example, the central management AP finds other child APsaround AP-a by querying AP-a's stored topology structure, and notifiesthe terminal (via AP-a). Accordingly, the terminal finds AP-b andestablishes a virtual connection therewith. In another alternative, thecentral management AP notifies other child APs around AP-a by queryingthe nearby APs topology structure and utilizes AP-a to store thattopology structure information. When the terminal establishes aconnection with AP-a, AP-a notifies the terminal. Accordingly, theterminal finds AP-b, and establishes a virtual connection therewith. Inthis embodiment, after the terminal establishes a virtual connectionwith AP-b, the connection information is stored in the terminal, asshown in second row of the above Table 3. In a similar way, theinformation is also stored in connection pool of the central managementAP, as shown in second row of the above Table 1.

It should be noted that, in certain embodiments, information in Tables1, 2 and 3 are not invariable, during operation. As such, in someembodiments, the terminal periodically or non-periodically updatesinformation in Tables 1, 2 and 3 either actively or according to signalsreceived from one or both of AP-A and AP-a.

A flowchart of a method for handing off a terminal among a plurality ofwireless APs, according to an embodiment of the invention, is describedbelow with reference to FIG. 3. Wherein, a plurality of wireless APs isconnected to a central management AP through one or both of wired orwireless connections.

In step S310, the central management AP receives network conditioninformation of a terminal communicatively connected to a first wirelessAP in the plurality of wireless APs. According to one embodiment, incase that the terminal is communicatively connected to a wireless AP,the parent AP acquires network condition information about the terminalthrough a wireless AP communicatively connected to (i.e. being in realconnection with) the terminal.

In one embodiment, network condition information of the terminalreceived by the central management AP includes one or both of i) networkcondition information of the terminal stored in the first wireless AP,and ii) network condition information of the terminal stored in theterminal and forwarded to the first wireless AP by the terminal.

In one embodiment, network condition information of the terminalincludes, for example, information such as AP name of a AP to which theterminal is connected, AP media access control layer (MAC) address,quality of a channel connected to AP, and whether connection with the APis a real connection or not.

In this embodiment, in step S320, the parent AP determines a secondwireless AP in the plurality of wireless APs to which the terminal is tobe handed off based on the network condition information of theterminal, wherein the second wireless AP is virtually connected to theterminal.

As mentioned above, a virtual connection refers to a connection throughwhich there is no data transmission between the terminal and a wirelessAP. In one scenario, the parent AP includes data that indicates thechannel quality of the first wireless AP (currently communicativelyconnected to the terminal) and channel quality of other wireless APs(virtually connected to the terminal via the received network conditioninformation of the terminal). In this embodiment, based, at least inpart, on such connection information, it is determined whether there isa need to hand off the connection to other wireless APs and, if so, towhich wireless AP the terminal should be handed off to.

For example, in case that the terminal is communicatively connected toAP-a and is virtually connected to AP-b and AP-c, it is determinedwhether handoff is needed by comparing channel quality of the firstwireless AP (i.e. AP-a) with a certain threshold. If AP-a's channelquality is lower than that specified by the certain threshold, then itis determined that there is a need to perform the handoff. As such, anAP having better channel quality that of AP-a is selected for handingoff by comparing the channel quality of AP-b and that of AP-c to that ofAP-a. In some embodiments, the difference in channel quality must exceeda threshold before such a handing off occurs. For example, by comparingchannel quality of AP-a and that of other wireless APs that are virtualconnected to the terminal (such as AP-b or AP-c), and determiningwhether the difference between them exceeds a certain threshold, it isdetermined whether handoff is needed. In practice, those skilled in theart may select various suitable manners to determine a wireless AP towhich the terminal is to be handed off to according to actual need of asystem.

In this embodiment, in step S330, the parent AP submits a handoffrequest to the second wireless AP. In one embodiment, information aboutthe terminal such as identification (ID), MAC address of the terminaletc., is included in the handoff request.

In this embodiment, in step S340, the parent AP notifies the terminal ofhanding off from the first wireless AP to the second wireless AP inresponse to receiving a handoff response from the second wireless AP.

According to an embodiment of the invention, the parent AP provideschannel information of the second wireless AP to the terminal via thefirst wireless AP currently in virtual connection with the terminal. Inthis embodiment, the terminal replaces channel information of the firstwireless AP with channel information of the second wireless AP to handoff to the second wireless AP. In this embodiment, the channelinformation includes the MAC address of the wireless AP. In addition, insome embodiments, the channel information further includes operatingfrequency, channel quality etc.

According to an embodiment of the invention, the parent AP updates andmaintains communication condition information in response to theterminal handing off to the second wireless AP. In this embodiment,after the terminal hands-off to the second wireless AP, the secondwireless AP notifies the parent AP, which includes informationindicating that the handoff is completed. In response, the parent APupdates information in the maintained connection pool of the parent APafter receiving the notification from the second wireless AP. In thisembodiment, the parent AP also issues a notification to the firstwireless AP, which indicates to the first wireless AP connection betweenthe first wireless AP and the terminal has been handed off to the secondwireless AP. In this embodiment, in response to receiving such anindication, the first wireless AP clears its stored information aboutthe terminal.

In this embodiment, with the above method, delay and even networkdisconnection due to handoff in wireless network is reduced. Inaddition, there is a reduction of poor user experience due to slownetwork speed (in case of poor channel quality) Further, the problem ofhigh transmission power needed while the terminal is in communicationwith an AP due to poor signal quality is reduced. In some cases,interference due to ambient wireless networking signals is also reduced.

FIG. 4 depicts a diagram of an example of a flow for handing off aterminal among a plurality of wireless APs according to an embodiment ofthe invention.

As shown in FIG. 4, AP-A is a parent AP, the terminal is a computer,AP-a is a network access point currently having poor signal, AP-b is anetwork access point having better signal. In the case where the parentAP determines that AP-a has poor signal (eg., the signal quality fallsbelow a minimum threshold), the parent AP finds and assigns a betterconnection (e.g., AP-b) to the computer. FIG. 4 illustrates a procedurefor handing off the computer from AP-a to AP-b.

In this embodiment, tables stored in various child APs before handoffare shown as Tables 4-1 and 4-2 below. In this embodiment, the parent APfrequently checks network condition of the terminal. As shown in FIG. 4,AP-A sends a channel quality measurement request to AP-a. In response,AP-a forwards this request to a terminal communicatively connectedtherewith. The terminal returns a channel quality measurement report toAP-a in response to receiving the request, and AP-a accordingly forwardsthe report to AP-A. In this embodiment, AP-A immediately updates itsstored connection pool to include the status of the child APs. In thisembodiment, when signal of a network actually communicatively connectedto the terminal is far poorer than (such as, lower than a threshold)that of other connectable network such as AP-b, it is determined that anetwork handoff needs to be performed. At this point, AP-A sends ahandoff request to AP-b, and information such as MAC address of theterminal etc., is contained in the handoff request. If AP-b is capableof accepting the terminal, AP-b sends a response of approving thehandoff request to the parent AP. After receiving the response, theparent AP sends a handoff command to AP-a, to tell AP-a to make theterminal hand off to AP-b, and confers other information, such as MACaddress of AP-b etc., to the terminal via AP-a.

In this embodiment, after the terminal receives the handoff command ofAP-a and MAC address of AP-b, the terminal hands the communicationconnection off to AP-b by replacing MAC address of AP-a with MAC addressof AP-b. In this embodiment, the terminal also adds a connection recordin stored table of AP-b. Once AP-b has completed handoff, AP-b reportsto the parent AP (in this case AP-A). Finally, the parent AP sends aninstruction to AP-a, notifying AP-a that the terminal has been connectedto AP-b. In response, AP-a confirms that information associated with theterminal has been cleared form AP-a, and the whole handoff procedure iscompleted after the clearance is completed. At this point, the resultingtables stored in child APs are shown below as Tables 5-1 and 5-2.

TABLE 4-1 Information of terminal stored in AP-a Channel ReceivedTerminal Terminal Terminal quality signal strength No. name MAC address(dB) (dBm) MS-1 test-23xx 44-45-53-54- 3 −77 00-00

TABLE 4-2 Information of terminal stored in AP-b Terminal TerminalTerminal Connection No. name MAC address speed

TABLE 5-1 Information of terminal stored in AP-a Terminal TerminalTerminal Connection No. name MAC address speed

TABLE 5-2 Information of terminal stored in AP-b Received TerminalTerminal Terminal Channel signal strength No. name MAC address quality(dB) (dBm) MS-1 test-23xx 44-45-53-54- 20 −60 00-00

In the diagram shown in FIG. 4, it is the parent AP that activelyacquires network connection condition of a terminal. In this embodiment,the parent AP actively initiates handoff procedure in case that networkcondition is poor. However, it will be appreciated by those skilled inthe art that, the terminal or a child AP in middle layer (such asAP-a/b/c) may also initiate handoff of network connection based oninformation about channel quality.

For example, according to an embodiment of the invention, a terminalactively initiates the handoff procedure. In one embodiment, while incommunication with an AP, the terminal also periodically probes channelquality of other APs. Alternatively, in one embodiment, in order to saveenergy, channel quality probation on other APs is triggered when it isdetermined that channel quality of the current AP has degraded. In sucha case and in one embodiment, while keeping communication connectionwith AP-a, the terminal scans connection condition of other APsvirtually connected thereto. When it is determined that there is an AP-bthat has better channel quality, a handoff request is actively made toparent AP (AP-A) via AP-a. In one embodiment, in case that AP-A receivesthe handoff request, it is confirmed by AP-b whether such a handoff canbe performed (based, at least in part, on system limitations). Thesubsequent flow and processing is substantially similar to thatdescribed above and is omitted here for brevity.

In some embodiments, scanning of channel quality by a terminal isperformed using a different process. According to one embodiment of theinvention, when a terminal is scanning channel quality, the terminalscans all the possible operating frequency bands to identify all the APsaround that terminal. However, in some embodiments, such a scan istime-consuming, consumes high energy, and occupies a relatively longnetwork communication time.

According to one embodiment, a parent AP determines the approximateposition of a terminal using a combination of techniques, such aswireless positioning etc, and actively notifies the terminal ofinformation of APs that are adjacent to the parent AP. The parent APthen approximates the distance to those APs and the network topology ofchild APs managed by the parent AP. In some cases, a terminal isinstructed to perform a directional scan, which reduces number of APsbeing scanned and number of times a terminal scans APs. In certainscenarios, this approach results in at least one of: i) a reduction inpower consumption by the terminal, and ii) an improvement in theeffective communication time of the terminal with current AP.

At least one embodiment of the present invention manages a plurality ofAPs, located within a same public area, by setting up a centralmanagement AP. Such an embodiment has access to information indicatingthe status of those managed APs, and acquires channel qualityinformation of each mobile terminal. In addition, in some embodiments, amobile terminal also scans for available APs to which connection can bemade. In some embodiments, even if the mobile terminal has beenconnected to a network, that mobile terminal can still receive signalsfrom other APs and establish virtual connection therewith. In someembodiments, when the mobile terminal needs to change to a differentnetwork, it only needs to alter MAC address of an AP in a MAC packet,thereby completing a soft handoff which, in some cases, is apparent tothe user of the mobile terminal. In this way, certain embodiments enablethe mobile terminal to receive signal having the best available quality.

FIG. 5 depicts a block diagram of a system for handing off a terminalamong a plurality of wireless APs according to an embodiment of theinvention.

As shown in FIG. 5, the system 500 comprises a number of modules, whichin FIG. 5 are denoted as “means”. Such modules include one or both ofthe hardware and software (e.g., programming and logic) to perform oneor more processes included in the method described in the previoussections. In this embodiment, such modules include: a receiving means510, a handoff determining means 520, a handoff requesting means 530 anda handoff notifying means 540. The receiving means 510 is configured toreceive network condition information of a terminal communicativelyconnected to a first wireless AP in the plurality of wireless APs. Thehandoff determining means 520 is configured to determine a secondwireless AP in the plurality of wireless APs to which the terminal is tobe handed off based on the network condition information of theterminal. The second wireless AP is virtually connected to the terminal.The handoff requesting means 530 is configured to submit a handoffrequest to the second wireless AP. The handoff notifying means 540 isconfigured to notify the terminal to hand off from the first wireless APto the second wireless AP in response to receiving a handoff responsefrom the second wireless AP.

According to an embodiment of the invention, the handoff notifying means540 further comprises: one or more modules (not shown) that areconfigured to provide channel information of the second wireless AP tothe terminal via the first wireless AP. The terminal replaces channelinformation of the first wireless AP with channel information of thesecond wireless AP to hand off to the second wireless AP. The channelinformation is MAC address of a wireless AP.

According to an embodiment of the invention, the receiving means 510receives network condition information of terminals stored in the firstwireless AP.

According to an embodiment of the invention, the receiving means 510receives network condition information of terminals stored in theterminal and forwarded to the first wireless AP by the terminal.

According to an embodiment of the invention, the system 500 furthercomprises modules (not shown) configured to update maintained networkcondition information in response to the terminal handing off to thesecond wireless AP.

According to an embodiment of the invention, the system 500 furthercomprises modules (not shown) configured to notify the first wireless APto clear information about the terminal therein in response to theterminal handing off to the second wireless AP. The network condition ofthe terminal includes channel quality information.

According to an embodiment of the invention, the handoff determiningmeans 540 comprises: one or more modules configured to determine thatthe second wireless AP is a wireless AP to which the terminal is to behanded off to in response to a difference between channel qualityinformation of the second wireless AP and channel quality information ofthe first wireless AP exceeding a certain threshold.

According to an embodiment of the invention, the handoff determiningmeans 540 comprises: one or more modules configured to determine asecond wireless AP in the plurality of wireless APs to which theterminal is to be handed off based on the network condition informationof the terminal and network topology of the plurality of wireless APs.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

1. A method for handing off a terminal among a plurality of wirelessaccess points (APs), wherein the plurality of wireless APs is connectedto a central management AP, the method comprising: receiving, by one ormore processors, a network condition information of a terminalcommunicatively connected to a first wireless AP in the plurality ofwireless APs; determining, by one or more processors, a second wirelessAP in the plurality of wireless APs to which the terminal is to behanded off to based, at least in part, on the network conditioninformation of the terminal, wherein the second wireless AP is virtuallyconnected to the terminal; submitting, by one or more processors, ahandoff request to the second wireless AP; and notifying, by one or moreprocessors, the terminal to handoff from the first wireless AP to thesecond wireless AP in response to receiving a handoff response from thesecond wireless AP.
 2. The method according to claim 1, the methodfurther comprising: providing, by one or more processors, channelinformation of the second wireless AP to the terminal via the firstwireless AP, wherein the terminal replaces the channel information ofthe first wireless AP with channel information of the second wireless APto hand off to the second wireless AP.
 3. The method according to claim2, wherein the channel information is MAC address of a wireless AP. 4.The method according to claim 1, the method further comprising:receiving, by one or more processors, a network condition information ofterminals that is stored in the first wireless AP.
 5. The methodaccording to claim 1, the method further comprising: receiving, by oneor more processors, a network condition information of terminals that isstored in the terminal and forwarded to the first wireless AP by theterminal.
 6. The method according to claim 1, the method furthercomprising: determining, by one or more processors, a second wireless APin the plurality of wireless APs to which the terminal is to be handedoff to based, at least in part, on the network condition information ofthe terminal and network topology of the plurality of wireless APs. 7.The method according to claim 1, wherein the network conditioninformation of the terminal comprises channel quality information. 8.The method according to claim 7, wherein the step of determiningcomprises: determining, by one or more processors, that the secondwireless AP is a wireless AP to which the terminal is to be handed offto in response to a difference between channel quality information ofthe second wireless AP and channel quality information of the firstwireless AP exceeding a threshold.
 9. The method according to claim 1,the method further comprising: updating, by one or more processors,maintained network condition information in response to the terminalhanding off to the second wireless AP.
 10. The method according to claim1, the method further comprising: notifying, by one or more processors,the first wireless AP to clear information about the terminal therein inresponse to the terminal handing off to the second wireless AP.
 11. Asystem for handing off a terminal among a plurality of wireless accesspoints (APs), wherein the plurality of wireless APs is connected to acentral management AP, the system comprising: one or more computerprocessors; one or more computer readable storage medium; programinstructions stored on the computer readable storage medium forexecution by at least one of the one or more processors, one or moremodules including the program instructions, the one or more modulescomprising: a receiving module configured to receive network conditioninformation of a terminal communicatively connected to a first wirelessAP in the plurality of wireless APs; a handoff determining moduleconfigured to determine a second wireless AP in the plurality ofwireless APs to which the terminal is to be handed off based on thenetwork condition information of the terminal, wherein the secondwireless AP is virtually connected to the terminal; a handoff requestingmodule configured to submit a handoff request to the second wireless AP;and a handoff notifying module configured to notify the terminal to handoff from the first wireless AP to the second wireless AP in response toreceiving a handoff response from the second wireless AP.
 12. The systemaccording to claim 11, wherein the handoff notifying module furthercomprises: a module configured to provide channel information of thesecond wireless AP to the terminal via the first wireless AP, whereinthe terminal replaces channel information of the first wireless AP withchannel information of the second wireless AP to hand off to the secondwireless AP.
 13. The system according to claim 12, wherein the channelinformation is MAC address of a wireless AP.
 14. The system according toclaim 11, wherein the receiving module receives network conditioninformation of terminals stored in the first wireless AP.
 15. The systemaccording to claim 11, wherein the receiving module receives networkcondition information of terminals stored in the terminal and forwardedto the first wireless AP by the terminal.
 16. The system according toclaim 11, wherein the handoff determining module comprises: a moduleconfigured to determine a second wireless AP in the plurality ofwireless APs to which the terminal is to be handed off based on thenetwork condition information of the terminal and network topology ofthe plurality of wireless APs.
 17. The system according to claim 11,wherein the network condition information of the terminal compriseschannel quality information.
 18. The system according to claim 17,wherein the handoff determining module comprises: a module configured todetermine that the second wireless AP is a wireless AP to which theterminal is to be handed off in response to a difference between channelquality information of the second wireless AP and channel qualityinformation of the first wireless AP exceeding a certain threshold. 19.The system according to claim 11, the system further comprising: amodule configured to update maintained network condition information inresponse to the terminal handing off to the second wireless AP.
 20. Thesystem according to claim 11, the system further comprising: a moduleconfigured to notify the first wireless AP to clear information aboutthe terminal therein in response to the terminal handing off to thesecond wireless AP.